E0 257 - Software Architecture Y. Narahari Department of Computer Science and Automation Indian Institute of Science Bangalore - 560 012 INDIA

PROBLEM SET #4

Architectural Patterns

• What would be an optimal architectural pattern to use for each of the following applications. Provide brief reasoning. Attempt a high level architecture diagram in each case.

(a) An office automation system for, say, CSA office
(b) A simulation package for communication networks
(c) A web server
(d) A document editor of Lexi type (discussed in the book by Gamma et al)
(e) Groupware software (of the type discussed by Bharath Kumar in an earlier email)


• (Souce: Prof. YN Srikant). It is required to design the following systems. Suggest suitable architectures with justification. Draw a high level architecture diagram (with subsystems and connectors).

(a) A natural language understanding system
(b) A GUI-based tool for supporting OOAD
(c) A personal calendar with facilities for adding and deleting appointments over email. An alarm should be generated on the console (visual or audio), when the appointment is due in the next one hour.

• Compare the strengths and limitations of RMI, RMI/IIOP, and CORBA technologies.
• How can a technology like CORBA be used as part of a J2EE or a .NET application?
• What are the different mechanisms for messaging and communication in the CORBA technology?
• Give a simple application which needs the power of DII and DSI in CORBA.
• Let us say you have developed a Java component that can solve any given instance of the traveling salesman problem. You wish to deploy and use this as part of a CORBA system. Describe a step-by-step procedure for doing this.
• What is GIOP? What is IIOP?
• How are the following design patterns used in CORBA?

(a) Facade
(b) Adapter (object version and class version)
(c) Proxy


• Do you think web services (SOAP/XML) would offer a better alternative technology to CORBA? Why?
• Consider a scenario where one organization needs to talk to multiple other organizations (example: e-procurement, e-selling, etc.). How can SOAP/XML/ebXML/UDDI be used here. What infrastructure would be required by the individual companies?

• In the Lexi case study, why don't you use an abstract factory pattern to implement multiple window systems?
• How do you exemplify the following statement: Delegation makes composition as powerful for reuse as inheritance.
• The first column below has patterns and the second column has "design aspects" that the patterns let you vary. Find a correct match.
  • Proxy - interface to an object
  • Adapter - implementation of an object
  • Template method - when and how a request is fulfilled
  • Command - an algorithm
  • Bridge - steps of an algorithm
  • Strategy - how an object is accessed
  It is required to modify a class that cannot be modified conveniently (for example, source code may not be available, or any change may may cascade modifications to numerous existing classes). What would be a good design pattern to use in this situation. Explain with a diagram how the pattern accomplishes this.
• Explain the difference between

  (a) Mediator and Observer
  (b) facade and Mediator
  (c) Adapter and Decorator
  (d) Strategy and Decorator
  (e) Strategy and Template Method
  

• "Encapsulating variation" is a major pattern in design patterns. What aspect do the following patterns encapsulate?

(a) Strategy
(b) State
(c) Mediator
(d) Iterator


• Name a few patterns that use objects as arguments. In each case, state what is achieved by using objects as arguments.
• Which patterns decouple senders and receivers? How do they achieve?
• How do these following pattern pairs work together?

  (a) Composite and iterator
  (b) Memento and iterator
  (c) COR and template method
  (d) COR and command
  (e) Interpreter and state
  (f) Iterator and visitor
  (g) COR and composite
  (h) Composite and state
  (i) Composite and observer
  

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